Tag Archives: A. Nunnenkamp

Nano (?) diamonds used in mechanical system to control quantum states

We do end up back in the world of spin but, first, there are the nano (I think) diamonds in an Aug. 3, 2015 news item on Nanotechnology Now,

Scientists at the Swiss Nanoscience Institute at the University of Basel have used resonators made from single-crystalline diamonds to develop a novel device in which a quantum system is integrated into a mechanical oscillating system. For the first time, the researchers were able to show that this mechanical system can be used to coherently manipulate an electron spin embedded in the resonator – without external antennas or complex microelectronic structures. …

A July 16, 2014 University of Basel press release (also on EurekAlert), which originated the news item, provides more detail about the work,

In previous publications, the research team led by Georg H. Endress Professor Patrick Maletinsky described how resonators made from single-crystalline diamonds with individually embedded electrons are highly suited to addressing the spin of these electrons. These diamond resonators were modified in multiple instances so that a carbon atom from the diamond lattice was replaced with a nitrogen atom in their crystal lattices with a missing atom directly adjacent. In these “nitrogen-vacancy centers,” individual electrons are trapped. Their “spin” or intrinsic angular momentum is examined in this research.

When the resonator now begins to oscillate, strain develops in the diamond’s crystal structure. This, in turn, influences the spin of the electrons, which can indicate two possible directions (“up” or “down”) when measured. The direction of the spin can be detected with the aid of fluorescence spectroscopy.

Extremely fast spin oscillation

In this latest publication, the scientists have shaken the resonators in a way that allows them to induce a coherent oscillation of the coupled spin for the first time. This means that the spin of the electrons switches from up to down and vice versa in a controlled and rapid rhythm and that the scientists can control the spin status at any time. This spin oscillation is fast compared with the frequency of the resonator. It also protects the spin against harmful decoherence mechanisms.

It is conceivable that this diamond resonator could be applied to sensors – potentially in a highly sensitive way – because the oscillation of the resonator can be recorded via the altered spin. These new findings also allow the spin to be coherently rotated over a very long period of close to 100 microseconds, making the measurement more precise. Nitrogen-vacancy centers could potentially also be used to develop a quantum computer. In this case, the quick manipulation of its quantum states demonstrated in this work would be a decisive advantage.

Unfortunately, the researchers do not indicate the measurement scale for the diamonds so I’m guessing, given the descriptions, that these were nanoscale diamonds being used in the research.

In any event, here’s a link to and a citation for the paper,

Strong mechanical driving of a single electron spin by A. Barfuss, J. Teissier, E. Neu, A. Nunnenkamp, & P. Maletinsky. Nature Physics (2015)  doi:10.1038/nphys3411 Published online 03 August 2015

This paper is behind a paywall.

An efficient method for signal transmission from nanocomponents

A May 23, 2015 news item on Nanotechnology Now describes research into perfecting the use of nanocomponents in electronic circuits,

Physicists have developed an innovative method that could enable the efficient use of nanocomponents in electronic circuits. To achieve this, they have developed a layout in which a nanocomponent is connected to two electrical conductors, which uncouple the electrical signal in a highly efficient manner. The scientists at the Department of Physics and the Swiss Nanoscience Institute at the University of Basel have published their results in the scientific journal Nature Communications together with their colleagues from ETH Zurich.

A May 22, 2015 University of Basel press release (also on EurkeAlert) describes why there is interest in smaller components and some of the challenges once electrodes can be measured in atoms,

Electronic components are becoming smaller and smaller. Components measuring just a few nanometers – the size of around ten atoms – are already being produced in research laboratories. Thanks to miniaturization, numerous electronic components can be placed in restricted spaces, which will boost the performance of electronics even further in the future.

Teams of scientists around the world are investigating how to produce such nanocomponents with the aid of carbon nanotubes. These tubes have unique properties – they offer excellent heat conduction, can withstand strong currents, and are suitable for use as conductors or semiconductors. However, signal transmission between a carbon nanotube and a significantly larger electrical conductor remains problematic as large portions of the electrical signal are lost due to the reflection of part of the signal.

Antireflex increases efficiency

A similar problem occurs with light sources inside a glass object. A large amount of light is reflected by the walls, which means that only a small proportion reaches the outside. This can be countered by using an antireflex coating on the walls.

The press release goes on to describe new technique for addressing the issue,

Led by Professor Christian Schönenberger, scientists in Basel are now taking a similar approach to nanoelectronics. They have developed an antireflex device for electrical signals to reduce the reflection that occurs during transmission from nanocomponents to larger circuits. To do so, they created a special formation of electrical conductors of a certain length, which are coupled with a carbon nanotube. The researchers were therefore able to efficiently uncouple a high-frequency signal from the nanocomponent.

Differences in impedance cause the problem

Coupling nanostructures with significantly larger conductors proved difficult because they have very different impedances. The greater the difference in impedance between two conducting structures, the greater the loss during transmission. The difference between nanocomponents and macroscopic conductors is so great that no signal will be transmitted unless countermeasures are taken. The antireflex device minimizes this effect and adjusts the impedances, leading to efficient coupling. This brings the scientists significantly closer to their goal of using nanocomponents to transmit signals in electronic parts.

Here’s a link to and a citation for the paper,

Clean carbon nanotubes coupled to superconducting impedance-matching circuits by V. Ranjan, G. Puebla-Hellmann, M. Jung, T. Hasler, A. Nunnenkamp, M. Muoth, C. Hierold, A. Wallraff, & C. Schönenberger. Nature Communications 6, Article number: 7165 doi:10.1038/ncomms8165 Published 15 May 2015

This paper is behind a paywall.